Improvement in removing colors from leather



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Letters Patent N 100,997, dated March 22, 1870.

IIVIIIPIIROVIIMEN'J." IN REMOVING COLORS FROM-LEATHER.

The Schedule referred to in these Letters IPatenl: and making part of the same.

To all whom it may concern Be it known that I, EDWARD S. FRYE, of Salem, in the county of Essex and State of Massachusetts, have invented a Process of Clcaring Leather, or Removing the Coloring-lilatter therefrom; and I hereby declare that the lbllowing is a full, clear, and exact description thereof.

In the process of tanning, much coloring-matter, gums, and other foreign substancesoften pass into the hide with the tannic acid, rendering the leather dark colored, and injuring itsqnality.

This dark colored leather is much less desirable, and does not connnand so high a price as that of alight color, for the reason that it cannot be so generally used for all purposes to which the class of leather is adapted. y 1

' My invention has for its object to enable me to remove, or partially remove, the coloring-matter and other foreign substances from leather, so as to render it light colored, and consistsin subjecting the leather first to an alkaline solution, which extracts the coloring natter, 860., and afterwards to an acid solution, which removes itfrom the surface of the leather, so that itscolor and general appearance when dry will be improved to a great degree, while no injurious effects are produced upon the leather, as the alkali and acid neutralize each other.

To enable others skilled in the art to understand and use my invention, I will proceed to describe the manner in which I have carried it out.

I first make an alkaline solution by dissolving from six to seven pounds of Sal-soda, inoue hundred gab. lons of water, at a temperature of about 100 Fahrenheit. The leather is then dipped into this-alkaline solution, and after being removed therefrom is innuediately dipped into a solution formed by mixing from six to seven pounds of sulphuric acidwith one hundred gallons of water. The leather is then removed, rinsed in cold water, and hung up to dry.

The alkaline solution partially extracts the coloringmatter, gums, and other 'foreign substances, which have passed into the leather with the tannicacid during the process of tanning, and the acid removes this matter from its surface, so that when dry it will be clear and bright, and of a much lighter color than before being treated, no injurious elfects being produced upon the leather, as the alkali and acid neutralize each other, while the removal of the coloring-matter, gums, &'c., greatly improves the quality of'the leather.

By means otithe above process, dark-colored leather, I Y which could only be used for inferior purposes, can be partially decolorized or rendered many shades lighter than before, in consequence of which it will be much more saleable, andwill command a higher price than it would before being treated, as it can bccmployed for any purpose to which the class of leather is applicable.

I prefer to use sal-soda and sulphuric acid, as they are the cheapest alkali and acid, but any chemical equivalents thereof in the proper proportions may be used instead. p

I iind in practice that it is sufficient to dip the leather into the alkaline and acid solutions, and allow it to remain in each for a few moments only.

Instead of treating the leather after being tanned, it may be removed from the vat while being tanned, and subjected to my decolorizing process, which will open the pores of the leather, so that more tauuic acid will be admitted, which willrender the leather more solid, and thereby improve its quality.

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1870. EDWARD S. FRYEL Witnesses:

P. E. TESOHEMACHER,

W. J. CAMBRIDGE. 

